In recent years, a GaN-based compound semiconductor has become a focus of attention as a semiconductor material for a short-wavelength light emission element. A GaN-based compound semiconductor uses various oxides or III-V compounds starting with single-crystal sapphire as a substrate, and is formed on the substrate by metal organic chemical vapor deposition (MOCVD method), molecular beam epitaxy (MBE method) or the like.
In such a semiconductor light emission element using a GaN-based compound semiconductor, multi-layered semiconductor layers having an LED structure that is formed of an n-type semiconductor layer, a light emission layer and a p-type semiconductor layer are typically formed on a substrate. A transparent electrode and a pad electrode for bonding are then formed on the uppermost p-type semiconductor layer, while a pad electrode for bonding is formed on the n-type semiconductor layer exposed by removing a part of the p-type semiconductor layer and the light emission layer by means of etching or the like.
As a conventional art described in an official gazette, there is known a structure in which a pad electrode (connection electrode) for bonding having a certain degree of thickness is arranged in some region on a transparent electrode made of a metal oxide such as ITO (see Patent Literature 1). Additionally, this Patent Literature 1 describes that the pad electrode on the transparent electrode is formed of Au/Cr, and a pad electrode on an n-type nitride semiconductor layer is formed of Au/Cr.